The magnetic recording media in common use today typically comprise, as the binder component, thermoplastic resins such as vinyl chloride-vinyl acetate, vinyl chloride-vinylidene chloride, cellulose, acetal, urethane, acylonitrile-butadiene and other resins, either used alone or in combination. However, the magnetic layers thus formed are not sufficiently resistant to abrasion; thus the tape-head environments are readily fouled.
It is also a known technique to employ thermosetting resins such as melamine-formaldehyde and urea-formaldehyde resins or use a cross-linking chemical such as an isocyanate or epoxy compound in combination with thermoplastic resins. However, when a cross-linking binder is employed, the following disadvantages are inevitable. (1) The resin solution including a dispersion of magnetic particles has a poor aging stability, i.e. a short pot life, so that the magnetic tape is not as homogeneous as may be desired. (2) After coating and drying, the coated surface must be heat-treated to harden the coated film with the result that a long production time is required.
The above-described magnetic recording media comprising, as the binder component, vinyl chloride-vinyl acetate resin, urethane resin or isocyanate compound are described in, for example U.S. Pat. Nos. 4,431,712, 4,411,956 and 4,333,988.
To overcome these disadvantages, Japanese Patent Publication No. 12423/72, and Japanese Patent Publication (unexamined) Nos. 13639/72, 15104/72, 77433/75 and 25231/81 (corresponding to U.S. Pat. No. 4,443,490), for instance, teach techniques of using an acrylic acid ester oligomer and monomer system as the binder, and, after-drying, effecting a cure with electron beams. However, none of the above techniques provides a magnetic recording medium having sufficiently desirable magnetic properties (electromagnetic conversion characteristics) and running life characteristics.
The recent prolongation of tape recording times demands a thin support and improved dynamic properties in the magnetic layer. In the case of a video tape, for instance, the recent multi-functionality of video cassette recorders imposes rugged use conditions on the magnetic tape. Conventional techniques are incapable of providing a magnetic layer having dynamic properties commensurate with such requirements.